Field of the Invention
The present disclosure relates to a see-through organic light emitting display device and a method for manufacturing the same, and more particularly, to a see-through organic light emitting display device in which an area of a see-through region is maximized by using a transparent auxiliary electrode and a method for manufacturing the same.
Description of the Related Art
An organic light emitting display device is a self-light emitting display that does not need a separate light source unlike a liquid crystal display device. Thus, the organic light emitting display device can be manufactured into a lightweight and thin form. Further, the organic light emitting display device is advantageous in terms of power consumption since it is driven with a low voltage. Also, the organic light emitting display device has a high response speed, a wide viewing angle, and an infinite contrast ratio. Therefore, the organic light emitting display device is considered to be a next-generation display device.
Since the organic light emitting display device can be easily manufactured into a thin form, it can be used as a see-through display device which is transparent and capable of displaying an image. A see-through organic light emitting display device includes a light emitting region where sub-pixels each including an organic light emitting element are disposed and a see-through region configured to transmit a background view through the organic light emitting display device. In order to increase the transmissivity (transparency) of the see-through organic light emitting display device, an area of the see-through region needs to be maximized. Particularly, as the resolution of the see-through organic light emitting display device is increased, the number of sub-pixels is increased, and the number of lines for driving the sub-pixels is also increased in proportion to the increase in the number of sub-pixels. Thus, there is a difficulty in securing a sufficient area of the see-through region. Particularly, if the transmissivity is too low, the background view perceived through the see-through display may be too dim.
A top-emission organic light emitting display device uses a transparent electrode or a translucent (semi-transparent) electrode as an upper electrode (e.g., a cathode) in order to emit light from an organic light emitting layer to an upper side, and translucent can refer to a semi-transparent property. A VSS voltage is applied to the cathode. Herein, in order to increase the transmissivity of the cathode, the cathode is formed to have a very thin thickness. However, a decrease in the thickness of the cathode causes an increase in a line resistance of the cathode.
Further, in a large-area organic light emitting display device, as a distance from a voltage supply pad is increased, a line resistance of a cathode is increased in proportion to the distance. Therefore, as the distance from the voltage supply pad increases, a voltage drop (or VSS rising) occurs more severely, which may cause non-uniformity in luminance of the organic light emitting display device. In the present disclosure, the term “voltage drop” refers to a decrease in a potential difference formed in an organic light emitting element, and more specifically, a decrease in a potential difference between an anode and a cathode of an organic light emitting element.
In other words, since a distance between each sub-pixel and a voltage supply pad varies, a line resistance of a cathode in each sub-pixel also varies. Therefore, a degree of voltage drop in each sub-pixel varies depending on a line resistance value of the cathode, resulting in non-uniformity in luminance of the organic light emitting display device.
In order to address such voltage drop issues, an auxiliary electrode may be used. The auxiliary electrode reduces a line resistance between a voltage supply pad and a cathode by electrically connecting the voltage supply pad with the cathode. However, since the see-through organic light emitting display device has a relatively narrow region in which the auxiliary electrode can be formed, the auxiliary electrode has a limit in reducing a line resistance of the cathode.
Further, since an incident angle at which a material to be used as an organic light emitting layer is deposited on an organic light emitting display panel is different depending on a position of a source for the material to be used as an organic light emitting layer, a voltage drop may occur differently in the overall organic light emitting display panel.
To be more specific, since the source of the organic light emitting layer is heated in a crucible and then deposited, an incident angle for deposition is determined on the basis of a position of the crucible within a chamber. If the material to be used as an organic light emitting layer is incident at an smaller angle than a reverse-taper angle of a partition wall, the organic light emitting layer is also formed in a region on the auxiliary electrode hidden by the partition wall. Therefore, an area of the organic light emitting layer which may be formed in the region on the auxiliary electrode hidden by the partition wall may vary, and a contact area between the auxiliary electrode and the cathode may also vary.
In particular, when the contact area between the cathode and the auxiliary electrode decreases, an overcurrent may flow in a narrow contact area causing undesirable heat to be created. Thus, a burnt defect may occur in the display device.
Accordingly, in order to secure luminance uniformity of the large-area top-emission organic light emitting display device regardless of a position of the organic light emitting display panel, there is a need of a method for uniformly maintaining the contact area between the auxiliary electrode and the cathode.